clinic: support '@' syntax for recursive mutexes

This adds support for protecting functions wrapped by argument clinic
with recursive mutexes or critical sections.

Author: colesbury

Tools/clinic/clinic.py

@@ -355,6 +355,9 @@ def __init__(self):
         # The C statements required to clean up after the impl call.
         self.cleanup = []
 
+        self.lock_statement = []
+        self.unlock_statement = []
+
 
 class FormatCounterFormatter(string.Formatter):
     """
@@ -822,7 +825,9 @@ def parser_body(prototype, *fields, declarations=''):
             # just imagine--your code is here in the middle
             fields.append(normalize_snippet("""
                     {modifications}
+                    {lock_statement}
                     {return_value} = {c_basename}_impl({impl_arguments});
+                    {unlock_statement}
                     {return_conversion}
                     {post_parsing}
 
@@ -862,7 +867,7 @@ def parser_body(prototype, *fields, declarations=''):
                     }}
                     """ % return_error, indent=4)]
 
-            if default_return_converter:
+            if default_return_converter and not f.lock:
                 parser_definition = '\n'.join([
                     parser_prototype,
                     '{{',
@@ -882,7 +887,7 @@ def parser_body(prototype, *fields, declarations=''):
                     {c_basename}({impl_parameters})
                     """)
 
-                if default_return_converter:
+                if default_return_converter and not f.lock:
                     # maps perfectly to METH_O, doesn't need a return converter.
                     # so we skip making a parse function
                     # and call directly into the impl function.
@@ -1373,6 +1378,14 @@ def render_function(self, clinic, f):
         selfless = parameters[1:]
         assert isinstance(f_self.converter, self_converter), "No self parameter in " + repr(f.full_name) + "!"
 
+        if f.lock is not None:
+            if f.lock == 'rlock':
+                data.lock_statement.append('_PyRecursiveMutex_lock(&{self_name}->{lock_name});')
+                data.unlock_statement.append('_PyRecursiveMutex_unlock(&{self_name}->{lock_name});')
+            else:
+                data.lock_statement.append('Py_BEGIN_CRITICAL_SECTION(&{self_name}->{lock_name});')
+                data.unlock_statement.append('Py_END_CRITICAL_SECTION;')
+
         last_group = 0
         first_optional = len(selfless)
         positional = selfless and selfless[-1].is_positional_only()
@@ -1474,6 +1487,10 @@ def render_function(self, clinic, f):
         template_dict['cleanup'] = format_escape("".join(data.cleanup))
         template_dict['return_value'] = data.return_value
 
+        template_dict['lock_name'] = f.lock
+        template_dict['lock_statement'] = "\n".join(data.lock_statement)
+        template_dict['unlock_statement'] = "\n".join(data.unlock_statement)
+
         # used by unpack tuple code generator
         ignore_self = -1 if isinstance(converters[0], self_converter) else 0
         unpack_min = first_optional
@@ -1497,6 +1514,8 @@ def render_function(self, clinic, f):
                 modifications=template_dict['modifications'],
                 post_parsing=template_dict['post_parsing'],
                 cleanup=template_dict['cleanup'],
+                lock_statement=template_dict['lock_statement'],
+                unlock_statement=template_dict['unlock_statement'],
                 )
 
             # Only generate the "exit:" label
@@ -2371,7 +2390,7 @@ def __init__(self, parameters=None, *, name,
                  module, cls=None, c_basename=None,
                  full_name=None,
                  return_converter, return_annotation=inspect.Signature.empty,
-                 docstring=None, kind=CALLABLE, coexist=False,
+                 docstring=None, kind=CALLABLE, coexist=False, lock=None,
                  docstring_only=False):
         self.parameters = parameters or collections.OrderedDict()
         self.return_annotation = return_annotation
@@ -2385,6 +2404,7 @@ def __init__(self, parameters=None, *, name,
         self.docstring = docstring or ''
         self.kind = kind
         self.coexist = coexist
+        self.lock = lock
         self.self_converter = None
         # docstring_only means "don't generate a machine-readable
         # signature, just a normal docstring".  it's True for
@@ -4362,10 +4382,12 @@ def state_modulename_name(self, line):
                 return
 
         line, _, returns = line.partition('->')
+        line, _, lock = line.partition(' @ ')
 
         full_name, _, c_basename = line.partition(' as ')
         full_name = full_name.strip()
         c_basename = c_basename.strip() or None
+        lock = lock.strip() or None
 
         if not is_legal_py_identifier(full_name):
             fail("Illegal function name: {}".format(full_name))
@@ -4418,7 +4440,7 @@ def state_modulename_name(self, line):
         if not module:
             fail("Undefined module used in declaration of " + repr(full_name.strip()) + ".")
         self.function = Function(name=function_name, full_name=full_name, module=module, cls=cls, c_basename=c_basename,
-                                 return_converter=return_converter, kind=self.kind, coexist=self.coexist)
+                                 return_converter=return_converter, kind=self.kind, coexist=self.coexist, lock=lock)
         self.block.signatures.append(self.function)
 
         # insert a self converter automatically